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Technical distributor question


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Hi again.

 

I am trying to fit an original Lucas distributor cap, where the currently installed one is an MGA one.

This means it is rotated by 90 degrees.

 

So obviously I can't just put the new cap on as the firing order and/or timing will be messed up.

So I assume I have to rotate the rotor. The rest of the distributor itself is aligned correctly as far as i can see.

 

I read all kinds of things online regarding timing lights and so on.

Since the car runs really well, is there just a simple way to adjust correctly, or is this really a more in-depth kind of operation?

For fun I could take the TR to 4800RPM in overdrive after a new clutch. Which I guess is around 90-95 mph. Not bad I thought!

I should perhaps also mention that the previous owner installed an electronic ignition of some sort, so no points.

 

Dirk

Edited by irrational
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That's what I thought, but this is an MGA cap:

 

post-535-0-52142100-1508185350_thumb.jpg

 

Side entry for all the leads. How are they anchored in, Dirk? The usual Lucas cap has push on leads, like this:

 

post-535-0-60916300-1508185476_thumb.jpg

 

If there is enough length just connect them to the plugs in the proper order, or else, can you detatch them and move them around?

John

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AFAIK the cap on the original DM2 distributor is side entry John - certainly it is on mine. There is a pointed screw on each terminal inside the cap which screws up into the wire to make the contact. It would be a bit more fiddly to swap the wires round than the push-on type but still pretty simple.

Edited by RobH
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Hi.

 

After Alan's comment I rechecked all the photos I could find of the original auto test etc.

Comparing many and tracing leads on old grainy photos

 

Wouldn't you know it, the MGA one seems to have had its wires fitted weird after all and changing them on the new cap will actually return them to the correct order. :P

Thank you very much Don H for your old unrestored TR2 photos! They very clearly showed where the leads should go.

 

Dirk

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The orientation of the cap on the distributor and the direction the side entry HT leads is (S) point is governed by where the cut out for the low tension terminal is (N) point . On a TR application it is originally opposite the HT lead outlets - They are, as to say N-S, when viewed from the side of the car. On other cars it could be in one of the other three possible positions - ie N-W, N-E, N-N. This takes the LT lead point cut out to be at N.

If you fit a N-W the HT leads head toward the radiator might fill with rain water, (very Mini) if N-N the HT leads will exit directly at the head/rocker cover.

 

Enjoy.....

Peter W

 

PS This 4 possibility of ways the HT leads will point, due to 4 basic types of cap design, ie where the cut out for the LT lead is goes in relation to the HT outlet, is lost once the later push in type top entry HT leads distributor cap was introduced - dropping the parts dept. stock holding permutations for spares to one type only to fit almost all the 25D or DM2 type distributor fitted cars.

Of course there are cars that need to side entry arrangement due to space limitations, but that will be a few only.

 

Notable is the Triumph Dolomite Sprint that uses a 45D distributor, (evolution of the 25D unit) and has a special side entry distributor cap, I'm told the regular top entry type of cap, just do not work.

Edited by BlueTR3A-5EKT
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"Notable is the Triumph Dolomite Sprint that uses a 45D distributor, (evolution of the 25D unit) and has a special side entry distributor cap, I'm told the regular top entry type of cap, just do not work."

 

Correct Peter, we found that out the hard way . . . . . the standard AC Delco dissie is a pretty poor thing, and even a new one certainly didn't want to handle the 7K rpm of Tom's Sigma-built 8-valve, hence switching to the Lucas unit. The Lucas dissie only works with the OE cap, end of story !

 

Cheers,

 

Alec

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